The survival of anaerobic bacteria at 4 degrees C and 22 degrees C on swabs in three transport systems. Statistical evaluation by application of a variance component model.

Abstract

The survival of anaerobic bacteria on swabs in three transport systems at 4 degrees C and 22 degrees C was evaluated. The transport systems were a charcoal-impregnated cotton swab in modified Stuart's transport medium (MS), a plain cotton swab in a dry aerobic tube (DA) and a plain cotton swab in an aerobic agar tube (AA). The test strains were Bacteroides fragilis, B. melaninogenicus ss. intermedius, Fusobacterium necrophorum, Peptostreptococcus anaerobius, Eubacterium lentum and Clostridium ramosum. Inoculated swabs were kept at the described conditions for time periods ranging from 22 1/2 min through 32 d, after which surviving organisms were recovered quantitatively. Results were described by the survival rate, defined as the percentage of organisms initially present, that had survived storage for 24 h. The survival rate was uniformly higher at 4 degrees C than at 22 degrees C. In Stuart's transport medium at 4 degrees C the survival rate was 81.9% compared to 4.3% in dry aerobic tube at 4 degrees C. At 22 degrees C the survival rate in dry aerobic tube and aerobic agar tube was 0.003% or less whereas in Stuart's transport medium growth occurred with B. fragilis, E. lentum and C. ramosum.